An investigative study on different magnetic ionic liquids to be used as a lubricant and sealant in a vacuum pump

Abstract

The aim of this work is to explore the possibility of using a magnetic ionic liquid as both a lubricant and sealant in a vacuum pump. The current lubricant in use is due to become obsolete due to incoming legislation on fluorinated compounds. The long-term goal is to use a magnetic field to hold the novel lubricant in place to create a better seal and thus reduce pressure more effectively whilst also lubricating the necessary mechanical parts. This paper explores physical properties (contact angle, viscosity, coefficient of friction (COF) and magnetism) and chemical properties (thermal stability and chemical stability as deduced by X-ray photoelectron spectroscopy (XPS)) of three ionic liquids based on imidazolium cations with varying length of alkyl side chain and a tetrachloroferrate anion along with two control lubricants which are used currently in the field and based upon perfluoropolyether (PFPE). The work shows that the three magnetic ionic liquids possess a lower COF value than the two control lubricants when measured using a Bruker UMT TriboLab suggesting they may perform better in the real life vacuum pump. Upon analysis of the three ionic liquid samples after tribological testing using XPS, it was shown that the ionic liquid samples displayed minor differences in spectra suggesting good stability with no obvious decomposition or degradation of the sample.